Field of the Invention
The present invention relates to a method and a system of determining suitability of correction for a control logic of a selective catalytic reduction (SCR) catalyst, and more particularly, to a method and a system of determining suitability of correction for a control logic of an SCR catalyst that secures reliability of correction executed on the control logic controlling operation of the SCR catalyst.
Description of Related Art
Generally, exhaust gas flowing out from an engine through an exhaust manifold is urged into a catalytic converter mounted at an exhaust pipe and is purified therein. After that, the noise of the exhaust gas is decreased while passing through a muffler and the exhaust gas is then emitted into the air through a tail pipe. The catalytic converter purifies pollutants contained in the exhaust gas. In addition, a particulate filter for trapping particulate matter (PM) contained in the exhaust gas is mounted in the exhaust pipe.
A selective catalytic reduction (SCR) catalyst is one type of such a catalytic converter.
Reducing agent such as urea, ammonia, carbon monoxide and hydrocarbon (HC) reacts better with nitrogen oxide than with oxygen in the SCR catalyst.
An exhaust system of a vehicle provided with the SCR catalyst includes an urea tank and dosing module. The dosing module injects reducing agent such as urea into the exhaust gas passing through the exhaust pipe, and thereby the SCR catalyst purifies the nitrogen oxide efficiently.
The reducing agent injected from the dosing module is absorbed in the SCR catalyst, is released when the exhaust gas containing the nitrogen oxide passes through the SCR catalyst, and reacts with the nitrogen oxide. when excessive reducing agent is injected from the dosing module, a portion of the reducing agent is not absorbed in the SCR catalyst and is slipped. Ammonia is typically used as the reducing agent of the SCR catalyst. When the ammonia is slipped from the SCR catalyst, the slipped ammonia may cause stink and customers may have complaints. When the dosing module injects the reducing agent insufficiently, the nitrogen oxide contained in the exhaust gas cannot be sufficiently removed and is exhausted to the exterior of the vehicle. Therefore, amount of the reducing agent injected from the dosing module should be precisely controlled.
In a conventional method of determining the amount of the reducing agent, the amount of the reducing agent according to driving conditions is stored in a map through experiments and the amount of the reducing agent according to current driving condition is determined from the map. However, since there are a millions of driving conditions affecting the amount of the reducing agent, manufacturing the map is a tedious and expensive process.
In addition, since the driving condition changes very quickly, a measuring apparatus has error, and experiments cannot be conducted under all the driving conditions when manufacturing the map, the map itself has error. In order to reduce the errors, the map is corrected. However, it is very difficult to get over innate limitations such as error of the measuring apparatus and quick change of the driving condition. Particularly, in a case that a vehicle runs on a road, a specific driving condition maintains for a very short time and an error determined under the specific driving condition does not necessarily reflect actual characteristics of the SCR catalyst.
Meanwhile, an error may not converge but diverges in a specific system when a control logic is corrected. In addition, a converging speed of the error may be very slow. In this case, resetting and newly correcting the control logic may be better than correcting the previously corrected control logic.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.